The present invention relates generally to image generating systems, and more particularly to optics arrangements and light source arrangements especially suitable for miniaturized image generating systems such as the miniaturized image generator disclosed in U.S. Pat. No. 5,748,164 entitled ACTIVE MATRIX LIQUID CRYSTAL IMAGE GENERATOR, which is incorporated herein by reference.
One of the ongoing challenges facing the manufacture of miniature image generating systems is providing smaller and smaller systems. Miniature image generating systems which are small enough to be mounted onto a helmet or small enough to be supported by a pair of eyeglasses will find a wide variety of uses if they can provide adequate resolution and brightness in a small, low-power package at a low cost. Conventional technologies such as CRTs are difficult to miniaturize and therefore do not hold much promise in this field. Alternatively, new systems based on VLSI integrated circuits are currently being developed which provide much smaller spatial light modulators for use in a miniaturized image generating systems. However, one of the problems in this field is providing optics and illuminating arrangements which may be scaled down in coordination with the miniaturized spatial light modulator in order to provide an overall image generating system which is practical and compact enough to be mounted onto a helmet or supported by a pair of glasses. Another problem in this field is providing an illuminating arrangement which requires as little power as possible in order to make the overall system more portable.
Referring to FIG. 1, a prior art miniature image generator system generally designated by reference numeral 10 will be described. System 10 includes a transmissive spatial light modulator 12 which modulates light from a light source 14 positioned immediately adjacent to spatial light modulator 12 by selectively changing the polarization of light passing through the spatial light modulator. A polarizer 16 is positioned between light source 14 and spatial light modulator 12 which allows light of one polarization from light source 14 to enter spatial light modulator 12. An analyzer 18 is positioned adjacent to the opposite side of spatial light 12 which allows light of a particular polarization to pass through analyzer 18. An eyepiece lens 20 having a focal length F1 is positioned approximately one focal length F1 from spatial light modulator 12 such that a viewer may see a virtual image of the pattern of modulated light formed by spatial light modulator 12 when the viewer's eye is positioned in an appropriate location. As shown in FIG. 1, this arrangement results in a viewing region indicated by reference numeral 22 from which a viewer may view the entire virtual image of the pattern of modulated light produced by the spatial light modulator display.
In the above described arrangement, since light source 14 is positioned adjacent to spatial light modulator 12, light source 14 must have a light emitting surface with essentially the same surface area as spatial light modulator 12. Also, in order for the optics to perform properly, the light source is a diffuse light source. However, these requirements causes two major problems. First, a large diffuse light source as described above is substantially more expensive than other types of light sources. Second, because light source 14 is diffuse, a large percentage of the light generated by light source 14, indicated by lines 24, is directed to areas which are not within viewing region 22 including areas in which the light does not pass through eyepiece lens 20. This wastes a large percentage of the light produced by light source 14 and requires much more light to be produced than would be necessary if substantially all of the available light were directed into viewing region 22. This wastage of light significantly increases the power requirements of the overall system. As will be seen hereinafter, the present invention provides a variety of novel optics arrangements including novel light source arrangements which, when combined with miniaturized spatial light modulators, are capable of providing low power, compact miniaturized image generating systems that may be used to produce a direct view miniature display.